The present invention relates to an ultrasonic motor used for driving printers, paper feeders, machine tools, camera zoom mechanisms, and the like and, more particularly, to an ultrasonic motor of a type such that a rectangular periodically vibrating member is supported and pressurized.
In recent years, an ultrasonic motor has been known in which a driving signal of a predetermined frequency is generated by a variable oscillator, and the driving signal is applied to a piezoelectric element via a power amplifier, by which traveling waves are generated on a vibrating body connected to the piezoelectric element to move a moving body touching the vibrating body with a predetermined pressure (for example, see Japanese Patent Publication No. Sho 62-92781).
In particular, an ultrasonic drive unit using elongation vibration and bending vibration of a rectangular piezoelectric vibrating plate (dual-mode vibrator), which is capable of effecting linear movement, rotational movement, etc. of a moving body by combined displacement of vibration mode, is expected to be used for various applications.
FIG. 13 shows an ultrasonic motor of a type using a rectangular vibrator.
This motor is made up of a piezoelectric vibrating body 14 vibrated by the application of a high-frequency voltage, a moving body 11 pressed on the vibrating body 14, a support member 26 for supporting the vibration node of the vibrating body 14, and a pressurizing member 33, which is pressed on both ends of the support member 26, for providing a pressurizing force to press the moving body 11 on the vibrating body 14 (see Jpn. J. Appl. Phys. Vol. 31 (1992) Pt. 1, No. 9BP3079).
With this unit, the moving body 11 is rotated by the combination of elongation vibration and bending vibration of the vibrating body 14.
FIG. 14 also shows an ultrasonic motor of a type using a rectangular vibrator.
This motor is made up of a vibrating body 14 consisting of multi-layer piezoelectric elements 14h and a vibrating portion 14i connected to the piezoelectric elements 14h, a cylindrical support member 26 locked to the vibration node of the vibrating body 14, protrusions 13 fixed on the lower side of the vibrating body 14, and a moving body 11 in contact with the protrusions 13 (see Jpn. J. Appl. Phys. Vol. 34 (1995) pp2756-2759).
With this unit, the moving body 11 is moved linearly in a fixed direction by elliptical vibrations of the protrusions 13 produced by the combination of elongation vibration and bending vibration of the vibrating body 14.
However, according to the aforementioned ultrasonic motor, because the pressurizing member 33 is needed in addition to the support member 26, there exists technical problems in that the configuration of the unit is complicated, the whole of the unit is large in size, and loss of vibration is liable to occur for the small vibration body 14.
Moreover, the aforesaid support member 26 is usually locked to the piezoelectric vibrating body 14 with a screw or pinning construction, so that the structural strength is not so high. Therefore, there arises a technical problem in that the pressurizing force provided to the support member 26 cannot be increased.
Further, the piezoelectric vibrating body 14 has a technical problem in that the moving direction of the moving body 11 is changed with respect to the target direction by a shift during assembly, nonuniformity of contact surface between the vibrating body 14 and the moving body 11, and the like.
Thereupon, the present invention was made to solve the above-mentioned technical problems, and accordingly an object thereof is to provide an ultrasonic motor in which the configuration of the unit is simplified and made compact, the support structure for the piezoelectric vibrating body is strengthened, and the change in moving direction of the moving body is prevented.